The present invention relates to the field of hand-held vacuum pumps, particularly of the type disclosed in U.S. Pat. Nos. 3,612,722, 4,775,302 and 4,806,084, by the present inventor Theodore C. Neward, the disclosures of which are incorporated herein by reference.
Vacuum pumps are generally useful whenever a vacuum is desired, for example, to provide suction. Many types of vacuum pumps have been devised, but they often suffer from such drawbacks as complexity, expense, excessive bulk, inability to pull a suitable vacuum, and the like. The vacuum pumps of the aforesaid patents have significantly solved the need for a vacuum pump which is simple, inexpensive, lightweight, compact and portable, and one which can pull a useful vacuum.
Such hand-held vacuum pumps are particularly useful in various industries, such as the automotive industry for vacuum system testing and repair, liquid sampling and the like. In the medical field, for example, such pumps have been used with vacuum extraction devices in childbirth, an aid for testing for throat blocking of choking victims, and other uses. Vacuum pumps manufactured according to the aforesaid patents have the ability to pull a vacuum of, for example, twenty-eight inches of mercury.
In many applications for such vacuum pumps it is particularly desirable to enable the vacuum which is developed by the pump to be easily and quickly released. Inasmuch as the hand-held vacuum pump is manually operated by hand, in many cases in the past it has been necessary to use the operator's second hand to operate a vacuum release mechanism that may be provided or used. As will be appreciated, this is cumbersome, especially when operating in a confined environment with limited maneuverability or when there are time restrictions. One solution to this problem is disclosed in the aforementioned U.S. Pat. No. 4,806,084 and which shows and describes a relatively simple vacuum release mechanism attached to the pump and which can be released relatively easily under finger control by the operator by a finger of the same hand that operates the pump. However, the improved vacuum release disclosed therein required that the operator position the release to the "on" position, or ensure that it was in this position, prior to operating the pump so that the vacuum can be drawn, and required that the release mechanism be manually returned by the operator to the "on" position after it was turned to the "off" position by the operator in releasing the vacuum. Thus, while this vacuum release facilitated one hand operation of the pump and one finger release of the vacuum (to the "off" or vacuum release position), it still was necessary to manually return the release to the "on" position, and thus sometimes could be cumbersome.